Mobile gantry cranes are often required to lift loads at four or more lifting points. In these cases, the crane is supplied with a dual trolley and hook block assembly. The typical dual trolley arrangement has an unadjustable fixed distance between the trolleys. This can be a disadvantage if the distance between the lift points on a product to be lifted varies. For this reason, a system that allows for the multiple trolleys to be independently powered so as to allow for an adjustment of the distance between lift points would be an important improvement in the art.